Hippocampal CA1 Neuronal and Sympathetic Nerve Activities in Response to Restraint Water‐Immersion Stress in Conscious Rats

Abstract

The hippocampus has been suggested to play a significant role in adaptation to chronic stress. However, there has been lack of direct evidence for responses of hippocampal neuronal activity to chronic stress. The present study was aimed to record hippocampal CA1 neuronal and sympathetic nerve activities during chronic stress. Wistar rats were instrumented chronically with a combined probe made with multiple electrodes (100 micrometer stainless steel wires) for measurement of hippocampal CA1 neuronal activity and glass fiber for measurement of hippocampal cerebral blood flow (CBF), electrodes for measurements of renal (RSNA) and lumbar (LSNA) sympathetic nerve activity, and electroencephalogram, electromyogram, and electrocardiogram and with catheter for measurement of systemic arterial pressure (AP). Rats were exposed repeatedly to restraint water‐immersion stress (RWIS) for 90 min/day over 5 days. Hippocampal CA1 neuronal activity, RSNA, and LSNA were measured continuously and simultaneously before, during, and after RWIS. Hippocampal CA1 neuronal activity decreased immediately after onset of RWIS and the decreased level was maintained throughout the 90 min of RWIS on the first day of stress exposure. On day 5 of RWIS, hippocampal CA1 neuronal activity decreased immediately after onset of RWIS, however it gradually recovered to the control level during the RWIS period. Thus, hippocampal CA1 neurons gradually adapted to the repeated RWIS exposure while RSNA and LSNA increased immediately after the onset of RWIS and showed no adaptive response during repeated exposure to RWIS.Support or Funding InformationJSPS GrantThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.